.TH std::mbrtoc32 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::mbrtoc32 \- std::mbrtoc32

.SH Synopsis
   Defined in header <cuchar>
   std::size_t mbrtoc32( char32_t* pc32,

                         const char* s,         \fI(since C++11)\fP
                         std::size_t n,

                         std::mbstate_t* ps );

   Converts a narrow multibyte character to its UTF-32 character representation.

   If s is not a null pointer, inspects at most n bytes of the multibyte character
   string, beginning with the byte pointed to by s to determine the number of bytes
   necessary to complete the next multibyte character (including any shift sequences).
   If the function determines that the next multibyte character in s is complete and
   valid, converts it to the corresponding 32-bit character and stores it in *pc32 (if
   pc32 is not null).

   If the multibyte character in *s corresponds to a multi-char32_t sequence (not
   possible with UTF-32), then after the first call to this function, *ps is updated in
   such a way that the next calls to mbrtoc32 will write out the additional char32_t,
   without considering *s.

   If s is a null pointer, the values of n and pc32 are ignored and the call is
   equivalent to std::mbrtoc32(nullptr, "", 1, ps).

   If the wide character produced is the null character, the conversion state *ps
   represents the initial shift state.

   The multibyte encoding used by this function is specified by the currently active C
   locale.

.SH Parameters

   pc32 - pointer to the location where the resulting 32-bit character will be written
   s    - pointer to the multibyte character string used as input
   n    - limit on the number of bytes in s that can be examined
   ps   - pointer to the conversion state object used when interpreting the multibyte
          string

.SH Return value

   The first of the following that applies:

     * 0 if the character converted from s (and stored in *pc32 if non-null) was the
       null character.
     * the number of bytes [1...n] of the multibyte character successfully converted
       from s.
     * -3 if the next char32_t from a multi-char32_t character has now been written to
       *pc32. No bytes are processed from the input in this case.
     * -2 if the next n bytes constitute an incomplete, but so far valid, multibyte
       character. Nothing is written to *pc32.
     * -1 if encoding error occurs. Nothing is written to *pc32, the value EILSEQ is
       stored in errno and the value of *ps is unspecified.

.SH Examples


// Run this code

 #include <cassert>
 #include <clocale>
 #include <cstring>
 #include <cuchar>
 #include <cwchar>
 #include <iomanip>
 #include <iostream>

 int main()
 {
     std::setlocale(LC_ALL, "en_US.utf8");

     std::string str = "z\\u00df\\u6c34\\U0001F34C"; // or u8"zß水🍌"

     std::cout << "Processing " << str.size() << " bytes: [ " << std::showbase;
     for (unsigned char c : str)
         std::cout << std::hex << +c << ' ';
     std::cout << "]\\n";

     std::mbstate_t state{}; // zero-initialized to initial state
     char32_t c32;
     const char* ptr = str.c_str(), *end = str.c_str() + str.size() + 1;

     while (std::size_t rc = std::mbrtoc32(&c32, ptr, end - ptr, &state))
     {
         std::cout << "Next UTF-32 char: " << std::hex
                   << static_cast<int>(c32) << " obtained from ";
         assert(rc != (std::size_t) - 3); // no surrogates in UTF-32
         if (rc == (std::size_t) - 1)
             break;
         if (rc == (std::size_t) - 2)
             break;
         std::cout << std::dec << rc << " bytes [ ";
         for (std::size_t n = 0; n < rc; ++n)
             std::cout << std::hex << +static_cast<unsigned char>(ptr[n]) << ' ';
         std::cout << "]\\n";
         ptr += rc;
     }
 }

.SH Output:

 Processing 10 bytes: [ 0x7a 0xc3 0x9f 0xe6 0xb0 0xb4 0xf0 0x9f 0x8d 0x8c ]
 Next UTF-32 char: 0x7a obtained from 1 bytes [ 0x7a ]
 Next UTF-32 char: 0xdf obtained from 2 bytes [ 0xc3 0x9f ]
 Next UTF-32 char: 0x6c34 obtained from 3 bytes [ 0xe6 0xb0 0xb4 ]
 Next UTF-32 char: 0x1f34c obtained from 4 bytes [ 0xf0 0x9f 0x8d 0x8c ]

.SH See also

   c32rtomb  convert a 32-bit wide character to narrow multibyte string
   \fI(C++11)\fP   \fI(function)\fP
   do_in     converts a string from ExternT to InternT, such as when reading from file
   \fB[virtual]\fP \fI\fI(virtual protected member function\fP of\fP
             std::codecvt<InternT,ExternT,StateT>)
   C documentation for
   mbrtoc32
